Salamanders and Frogs in Herrontown Woods--Spring Goings On

This is the third spring that the Friends of Herrontown Woods (FOHW) has helped frogs and salamanders safely cross Herrontown Road on their way to their breeding grounds in vernal pools. The work of the Princeton Salamander Crossing Brigade is documented in a blogpost on this site from last year, and in an article this week in the Town Topics. This year the Brigade was able to collaborate with Princeton's police department, which closed the road on one of the nights when the amphibians were on the move, dramatically reducing the customary carnage from road traffic down to zero. FOHW is hoping to collaborate similarly with the police department in the future.

Along with upcoming nature walks about amphibians during FOHW's Earthday celebration on April 13, I co-led an amphibian walk this past weekend, described below. Another walk I'm leading on April 5, through the Princeton Adult School, about plant life and forest ecology at Herrontown Woods will also touch on spring amphibian behavior and still has a few spots open. 

The walk at Herrontown Woods this past Saturday delved into the lives of frogs and salamanders along the ridge. We were fortunate to have two members of the Princeton Salamander Crossing Brigade with us. Inge Regan (second from left), who started the Brigade two years ago, is passionate about helping the frogs and salamanders safely migrate to their breeding grounds. This involves helping them avoid getting squashed by traffic when they cross the road on rainy nights in early spring. 

Neuroscientist and Crossing Brigade member Lisa Boulanger is very knowledgeable about amphibians, and brought along a couple red-backed salamanders she had found under a log that morning. These small but numerous salamanders don't need a vernal pool to lay their eggs. Lisa brought along the two color phases: red-backed and lead-backed.

Our first stop was a small pond we had dug in the Barden a couple years ago as part of a Zen Garden. I had placed a "refugia" in the bottom of the pond. An earthen pond in our piedmont clay will hold rainwater for days or even weeks, but ultimately the water seeps into the ground. Sinking a black plastic tub into the bottom of the minipond creates a refugia to sustain frogs and other water-loving creatures through droughts. This pond hosted adult green frogs and their young through last summer, and this spring during the walk, Lisa found a white glob of salamander eggs in the pond. Very flattering that the salamander community has found our little pond to be egg-worthy. (Info on mosquitoes and miniponds in this post.)

Nearby, not far from the parking lot, we stopped by a small but mighty vernal pool that holds water longer than others in the woods. This little pond was created naturally. Years ago, a tree blew over, and where its rootball had been, the depression for a vernal pool was created. The clay under this pool is so dense that the water doesn't seep in, but instead remains to sustain hundreds of frog and salamander larvae until they can grow to maturity. 

One curious observation we've made this year is that wood frog eggs, usually dominant in the vernal pools, are this year very few. No explanation for this scarcity as yet.

During the walk, Lisa was busily turning over logs in search of the most charismatic salamander in the woods, the spotted salamander. Finally, near a vernal pool deeper in the woods, she found one and showed it to all the participants. 

Lisa has taken many photos of the salamanders crossing the road on rainy nights, including the one below. You can see why these wild creatures are much loved.

A Special Bluff With Special Flora

There are places in nature that feel special in some way, places we find ourselves returning to. One special place for me is a bluff in the lower valley of Ellerbe Creek--a stream in Durham, NC for which I founded a watershed association a quarter century ago. 

During a recent visit, I took a walk with naturalist Cynthie Kulstad in one of the preserves we created back then, 80 acres called Glennstone Preserve. Cynthie is the botanist/horticulturist who helped sustain many of the plantings I had nurtured in parks and nature preserves while living there. The trails and our inclinations led us down to this special spot, on adjoining Army Corps of Engineers land.

Crowned by a massive white oak, the bluff is a collection of diabase boulders and uncommon plants overlooking the creek. 

One of those uncommon plants that makes this spot distinctive is resurrection fern (Pleopeltis polypodioides), all curled up and dried out on one of the boulders. Resurrection fern is an epiphyte, meaning it builds itself largely out of water and air, pluse whatever few nutrients collect on the rock it clings to from fallen leaves. Unlike most plants, this fern's leaves can dry out during droughts, then rapidly rehydrate after rains.

The only other place I've seen resurrection fern in Durham is on a similar but much larger bluff, where the Eno River just to the north encounters a mass of diabase rock and takes a sharp turn to the right, called Penny's Bend. I sense a kinship between these two bluffs, botanically and geologically. They could be called Big Bluff and Little Bluff, reflecting the respective size of the watersheds they are in.

(Up here in Princeton, NJ, with the same piedmont geology as Durham, a similar relationship can be seen between the big "Roaring Rocks" boulder field in the Sourlands and the boulder field in Princeton's Herrontown Woods, where the boulders are smaller and the water tends to chuckle and murmur rather than roar. These geologic features, too, are composed of diabase rock that resisted erosion through 200 million years.)

Looking up, I spotted another unusual native plant, eastern mistletoe (Phoradendron leucarpum), growing high on a tree branch. This one's a hemiparasite, meaning it extracts some sustenance from the tree but also has green leaves to make some of its own energy.

Other trees nearby also had dense balls of vegetation high up in the branches, but they weren't mistletoe. Those are witch's broom--a dense cluster of twiggy growth that is the tree's response to a pathogen or other irritant. Cynthie pointed out they are common on hop-hornbeam, a tree I hadn't seen in a long time and had been wanting to run into.

Turned out we were in the midst of a grove of eastern hop-hornbeam (Ostrya virginiana), growing along the edge of the bluff. (Upon returning to Princeton, I found some of these with their distinctive bark growing in Autumn Hill Reservation.)

Another tree nearby, judging from the leaves on the ground, was swamp chestnut oak (Quercus michauii). Paul Manos of Duke University calls these "sun leaves," meaning they are leaves that had been growing higher in the canopy and thus received a bigger dose of sunlight. They're smaller, thicker, and with sharper lobing than the more shaded leaves below.

I found more online about sun leaves and shade leaves, in a post by Gabriel Hemery:

"If there is some sunlight however, even a little diffuse light (see below), then a tree makes the most of it by producing shade leaves lower down in its canopy. Shade leaves are larger and thinner than normal sun leaves, and often appear a darker green (they contain more chlorophyll). They also have half as many stomata than sun leaves, or even fewer, and so have a lower respiration rate. They can react quickly to brief bursts of sunlight and dappled shade.

Shade leaves can turn into sun leaves and visa versa; providing that the change is gradual. This is something that a gardener moving a plant outside that has been grown indoors or in the greenhouse, must be aware of. When a plant is taken outdoors, place it first under shade and gradually over several days increase its exposure to bright sunlight." 

It would be interesting to know if pine needles, like those high up on this shortleaf pine, also vary according to how much sun they receive. 

During my eight years in Durham, plus many return visits over the years, I've found many special places along Ellerbe Creek. They could be as simple as a native azalea leaning out over the creek, or as complex and improbable as a roadside embankment packed with more than 100 native species of piedmont prairie. A few have been tragically destroyed, but it's heartening to return to those that persist, their charms sustained, their uniqueness unshattered by a rapidly changing world. These pockets of stability give my soul something to lean on.

Training Deer to Eat Invasive Plants -- Japanese Knotweed

Here's a story and a partially forgotten concept from ten years ago that a commenter on this blog helped me reconnect with. The concept has to do with actively training deer to eat invasive plants. Thanks to Mark Nowotarski of Stamford, CT for reminding me of this concept, and adding his own interesting twist.

Deer manage our landscapes with their appetites. Whether it's your unfenced yard or the local nature preserve, deer largely decide what can grow and what gets eaten down. Introduced plant species can become invasive if they are left uneaten by finicky deer, thus allowing them to proliferate rapidly and overwhelm native flora. Wouldn't it be great if we could train deer to eat invasive species, and thus restore balance to the landscape? 

Ten years ago, I wrote about two ways to potentially train deer to eat invasive species. One is to cut down invasive shrubs along the deer paths and let the stumps resprout, thus presenting the deer with tender new shoots to nibble on. As the deer (hopefully) grow accustomed to the taste and texture of the invasive's new growth, perhaps they would begin eating older foliage as well. 

It's also possible that the deer respond to visual cues. If we repeatedly cut back an invasive shrub, deer may assume other deer have been eating it, and chow down. Deer have reason to revisit a shrub again and again. By eating its foliage, they stimulate the shrub to replace the lost leaves with new ones, much as we do with basil and other vegetables in our gardens. Making their accustomed rounds, deer essentially farm the forest for fresh foliage.

Though we experimented with this at Herrontown Woods mostly with winged euonymus, Mark reports some success with recruiting deer to browse a patch of Japanese knotweed in his backyard:

"I've seen a similar phenomenon where I live in Stamford CT. We have a little bit of woods in the back yard where deer tend to congregate. There is a dense stand of Japanese knotweed down by a small stream. A few years ago, I started foraging the tips of the knotweed in the spring and noticed that the deer continued to browse the knotweed through the summer. Every time the knotweed would send out new shoots, the deer would browse the tips. At first they just browsed where I foraged, but in the past few years now they have expanded the browsed area and are actually beating back the knotweed. If you see any knotweed browsing in your area, I'd love to hear about it."

He sent photos and more text to illustrate:

"About 4 years ago, I noticed that the deer on our property had started browsing the spring shoots of a stand of Japanese knotweed. The knotweed grows down by a swampy stream and has been there for at least 30 years. Each year the deer have browsed the stand more intensely." 

"When the knotweed throws out side shoots after the initial browsing, the deer browse the tips of the side shoots. When the side shoots throw out secondary side shoots, the deer browse the tips of those as well. This continues through the summer."

"The knotweed in the browsed area is kept to about 3 feet tall and is very sparse. Abundant sunlight falls on the forest floor and there has been a substantial increase in the plant biodiversity of the browsed areas." 

"This includes the sprouting of native plants, such as Sassafras albidum (Sassafras) and Impatiens capensis (Jewel weed). I found the I. capensis particularly surprising since this is normally heavily browsed by the deer."

"The deer only browse a portion of the knotweed stand. If a knotweed shoot reaches full size, it’s not browsed. Nonetheless, each year the deer have been browsing a larger and larger area. They originally browsed just an outside edge of the stand where I used to forage knotweed shoots in the spring, but last year they started hollowing out the center of the stand." 

"Based on your experience with winged Euonymus, this leads me to suspect that it might have been my initial foraging that led the deer to continue the browsing. It would be interesting to forage some unbrowsed knotweed in the spring and see if the local deer continue."

Thanks again to Mark Nowotarski for these photos and descriptive text of the interesting dynamic between deer and the patch of invasive Japanese knotweed in his backyard. In our experiment ten years ago with winged euonymus, we found that invasive shrubs ultimately grew back, likely due to our having cut so many that their myriad young shoots overwhelmed the deer's mild interest in their foliage. We also didn't think to try focusing our cutting close to deer paths. 

Anyone managing a sizable nature preserve will soon grow weary of cutting invasive shrubs only to have them grow back. Treating a freshly cut stem with a thin film of systemic herbicide, using a Buckthorn Blaster, is a targeted, minimalist way of actually making progress in a woodland choked with invasive species. 

But especially for the vast majority of woodlands that go unmanaged, the concept of training deer to eat invasive species has appeal. I'm looking forward to harvesting some young shoots of Japanese knotweed this spring, as an experiment. Having trained the deer in his backyard to eat this highly invasive plant, Mark may train me to eat it as well. Testimonials like this one suggest the young shoots are quite tasty. Research the how, what, where and when before giving it a try. Mark recommends sauteing with butter.

Update 1.30.25: Just came across another of my posts from ten years back, entitled Paradox Lost, or, Less Irony in the Woodland Diet, offering a third way to get deer to eat invasive plants. If there are mint-flavored sprays that discourage deer from eating ornamental plantings, maybe there's a flavor of spray that would encourage them to eat invasive plants. 

Seeking "Lingering Trees"--Some Hope for Ash and Beech Trees

Most people attentive to nature are aware that Princeton has lost nearly all of its native ash trees over the past decade, and is now poised to lose its native beech trees as well. These are only the most recent losses due to assorted introduced insects, nematodes, and diseases against which our native trees had not evolved resistance. Also gone from the canopy over the past century are American chestnuts and American elms, with bacterial leaf scorch also taking a toll on red and pin oaks. As additional organisms enter the country due to an appalling lack of biosecurity, other species are threatened. 

What is there to do other than mourn, and mourn again, with each new wave of devastation? 

One answer to that question may be: Keep an eye out for "lingering" trees. It would be easy to assume that all our native ash, not having co-evolved with the Emerald ash borer (EAB), would be equally defenseless as the introduced larvae eat through the cambrium, cutting off the tree's circulatory system. But an initiative in Ohio has shown this not to be entirely true. Jennifer Koch, a research biologist with the USDA Forest Service, has been leading an effort to find "lingering ash", that is, mature ash that survive while others all around them succumb. Some ash that she and others have found have natural defenses that kill 20-45% of the larvae that bore into them. A very few trees kill 100% of the invading larvae. 

A very watchable video features Jennifer Koch, and also Holden Arboretum's Rachel Kappler, telling the 
story of ash lost, lingering ash found, and the effort to increase resistance among lingering ash through research and breeding programs.

One particularly impressive slide in the presentation showed how the resistant trees are able to stop the invading larvae before they do damage to the tree. 

 
Here are some of my notes from the video:

• Ash wood is/was used for bats and guitars
• Native ash species in our area: White, green, black, pumpkin
• 300 million acres of black ash-dominated forest in Minnesota could be lost (apparently no other tree species can survive in those wet areas)
• green ash is an important riparian buffer species in the plains states, hard to replace
• The lingering ash are found individually or in clusters, e.g Swan Creek, Oak Openings Park, near Toledo, 108 out of 11,000 had healthy canopies. Two specimens had no evidence of attack. Most resistance is partial, but resistance can be increased through breeding
• greenhouse tests can reduce the amount of land/labor needed for field tests
• resistance is inherited, though uneven

A central point these researchers make is how very limited is the area they have surveyed for lingering ash--only a small area near the Ohio/Michigan border. They call for similar initiatives in other parts of the country. 

That's where we come in, as keen or at least intermittently keen observers of the landscape through which we walk. It's important that any tree we believe to be lingering be a mature, wild tree--not a cultivar in a planted landscape--and that it be a tree that has weathered the massive wave of EAB over the past ten years, remaining green while others nearby have succumbed. Photos of lingering ash, and one story of their discovery, can be found at this link. 

A brief mention of the various species of ash: I associate white ash with higher ground and grander specimens found or once found around town. Green ash are less statuesque and more associated with wetter ground. Black ash I think of as growing, or having grown, in swamps, such as at Rogers Refuge in Princeton. The Ohio initiative is apparently finding most success with resistant green ash, though the video mentions lingering white, green, and black ash having been found in NY state.

In addition to the info below, there's also anecdata.org--a platform where citizen scientists can set up reporting initiatives.

This keeping an eye out for "lingering" ash can also be applied to other imperiled species in our area. The Ohio researchers request that people report lingering American beech, hemlock, and American elm as well. 

Related posts:

Emerald Ash Borer in Princeton

Beech Leaf Disease Sweeps Across Princeton

Holden Arboretum Studies Resistant Beech and Ash Trees